In this chapter we discuss conversational document search, which is to find relevant documents from document collections to meet user's information needs behind conversational search queries.
It is often referred to in a short form as conversational search, as documents are the most common form of system output. Differing from ad hoc search [1]}, conversational search systems need to take into account not only the input query but also conversational context when retrieving documents.
The retrieved documents can either be directly present to a user as the “ten blue links” in a search result page or be used as inputs to search result generation components e.g., to produce a concise summary using the query-focused summarization module or to generate a direct answer to the input query using the machine comprehension module. These search result generation modules will be described in the later chapters.
